This invention relates to electrically powered disk storage units and, in particular, to a low power consuming magnetic hard disk storage unit having multiple spindles and associated magnetic disks.
A hard disk drive (HDD) unit typically comprises a spindle, at least one disk platter rotatably supported by the spindle, at least one read-write head for reading/writing information from and to the disk platter(s), actuators for accurately positioning the read-write head(s) relative the disk platter(s) and an electronic controller for controlling the operation of the HDD. Various innovations have led to dramatic increases in the storage capacity and performance of (HDD) units and the miniaturization to smaller form factors. The storage capacity of HDDs has grown rapidly, historically exhibiting growth rates of 50 to 60% per year while showing growth rates of 130% per year in recent years. Almost as dramatic is the continuing reduction of the average cost per megabyte accompanying the increasing HDD capacities. The increased storage capacities and lower prices of HDDs have helped spur the proliferation of applications and devices using HDDs. While the storage capacities and costs of HDDs have improved, HDDs remain relatively power hungry as compared to other computer hardware devices. Furthermore, the power consumption requirements of HDDs is increasingly becoming more of a concern as the applications and devices using HDDs grow, especially for portable and mobile devices that rely on limited power sources such as batteries.
Of all the components comprising the typical disk drive unit, powering the rotation of the disk unit""s spindle is the single largest consumer of power. HDDs also require a greater amount of power during their startup since initiating the rotation of the magnetic disk platter(s) typically induces a current spike exceeding the normal operational power requirements of the HDD.
Attempts at reducing the -power consumption needs of a disk drive unit include reducing the size, particularly the diameter, of the magnetic disk platter(s). Less torque and power is typically required to initiate, maintain and stop the rotation of disk platter(s) having smaller diameters as compared to larger diameter disk platter(s). A disadvantage with decreasing the diameter of the disk platter(s) is that the readable/writeable surface area of disk platter(s) also decreases. While increases in areal density and decreases in recordable bit sizes continue to be researched and developed so that more data may be read-written onto smaller spaces, disk platter(s) having smaller diameters are capable of storing less data than similarly formatted larger diameter disk platter(s).
Another factor impacting the power consumption needs of a HDD is the rate of rotation for a spindle and the disk platter supported thereon. More power is generally required to rotate a disk faster than to rotate the same disk at a lower rate of speed. Currently, HDDs having rotation rates of 10,000 revolution per minute (rpm) are installed on desktop computers, and 5,000-7,000 rpm HDDs are used in laptop computers.
Therefore, more than continued miniaturization of HDD components is needed to achieve HDD power reductions while not sacrificing HDD performance or capacity.
It is known in the prior art to reduce the power consumption needs of a disk drive unit by reducing the diameter of the disk drive unit""s magnetic disks and starting only one disk at startup. European Pat. No. 671,741, published Sep. 13, 1995 entitled xe2x80x9cA Small Memory Unit With A Hard Diskxe2x80x9d, discloses housing either two 1.3xe2x80x3, three 1.0xe2x80x3 or four 0.7xe2x80x3 diameter magnetic platters in the same housing originally intended for a single 1.8xe2x80x3 diameter magnetic disk platter. Activating only one disk at the time of starting the disk operation reduces power consumption.
It is further known to house several smaller disk drives in a housing originally intended for a larger disk drive device. Japanese Pat. No. 6-084338, published Mar. 25, 1994 entitled xe2x80x9cArray Type Recording Devicexe2x80x9d discloses an array type configured disk storage device comprising multiple disk array units, each housed in standard sized 5.25xe2x80x3 enclosures for incorporating the array type disk array device in personal computers, etc. having standard 5.25xe2x80x3 computer expansion slots.
It is known to control the power consumption of a disk drive unit based on sequence control. Japanese Pat. No. 10-255451 published Sep. 25, 1998 entitled xe2x80x9cMethod for Supplying Power to Hard Diskxe2x80x9d discloses a power supply having a control function for controlling the power supplied to a plurality of HDDs based on sequence control.
It is known to provide multiple disk spindles on a single baseplate. Japanese Pat. No. 5-325496 published May 26, 1994 entitled xe2x80x9cDisk Devicexe2x80x9d discloses a disk storage device having two spindles on a single baseplate. The power consumption needs of the disk drive unit are reduced by an electric power control circuit that smoothes the power supply requirements of the disk drive unit.
The inventor has realized that a great majority of the information stored on hard disk drives, HDDs, is not frequently accessed for read-write purposes. Instead, only a relatively small percentage of a HDD is typically used to store the most frequently used data, such as commonly used operating system, data files, applications programs and modest data sets.
The present invention results from the further realization by the inventor that a low power consuming disk drive unit is effectuated by a disk drive unit having multiple HDDs and/or HDD subsystems of differing power consumption requirements and functioning as an integrated unit wherein only the more energy efficient HDD subsystem is selectively powered the majority of the disk drive unit""s operating time. As used herein, a HDD subsystem typically comprises at least one spindle, at least one disk platter rotatably supported by the spindle, at least one read-write head for reading/writing information from and to the disk platter(s), actuators for accurately positioning the readwrite head(s) relative the disk platter(s) and associated electronics and electronic controller which may be shared with other HDD subsystem(s). The more efficient HDD subsystem has smaller diameter disk platter(s) than the less efficient HDD subsystem(s), although other factors may also influence the power efficiencies of the HDDs. The multiple HDDs of the present invention function as an integrated device. The combined total storage capacity of the multiple HDD subsystems is typically comparable to, if not greater than, a conventional disk drive unit. Accordingly, the disk drive unit of the present invention has lower power consumption requirements without sacrificing performance or storage capacity.
The low power consuming disk drive unit comprises multiple HDD subsystems having different power consumption needs. Each HDD subsystem typically comprises a spindle, at least one disk platter rotatably supported by the spindle, at least one read-write head for reading/writing information from and to the disk platter(s), actuators for accurately positioning the read-write head(s) relative the disk platter(s) and an electronic controller for controlling the operation of the HDD subsystem. The smaller/more efficient HDD subsystem comprising the disk drive unit is typically used to store the most commonly accessed data while the less efficient/larger HDD subsystem (s) stores the less frequently accessed information. Note that, as used throughout this document, accessing information on a HDD and/or HDD subsystem encompasses both reading and writing information on a HDD.
Although smaller, the more efficient HDD subsystem is sufficiently sized to store the frequently accessed information so that there is no compromise in the disk drive unit""s performance. Since the smaller/more efficient HDD subsystem, stores the frequently used information, it is the smaller/more efficient HDD that is powered the majority of the time. The electronic controller controls the powering of the HDD subsystems and selectively powers only the smaller/more efficient HDD subsystem the majority of the time. Thus, the present disk drive unit achieves a reduction in power consumption needs.
The disk drive unit is also able to maintain the functionality, both capacity and performance, of a conventional disk drive unit having a single large HDD. The smaller/more efficient HDD subsystem stores the most frequently accessed information and typically has a faster seek time performance due to the smaller diameter of the disk platter(s). The larger/less efficient HDD subsystem(s) stores the less frequently accessed information. Combined, the smaller/more efficient HDD subsystem and the larger/less efficient HDD subsystem(s) may provide a storage capacity at least equal to, if not greater than, the storage capacity of a disk drive unit having a similarly formatted single large HDD. Additionally, the disk drive unit of the present invention is capable of improved performance since the most frequently accessed information is stored on the smaller HDD subsystem having improved seek time performance, as compared to a disk drive unit having a single large HDD similarly formatted. Therefore, the present invention provides a low power disk drive unit having reduced power consumption requirements and improved performance and capacity capabilities.